84 DISEASES OF GLASSHOUSE PLANTS 
from the following plants during the last three years: 
potato, tomato, cucumber, melon, sweet-pea, antirrhinum, 
and elm. Cross inoculations have demonstrated that 
the fungus from any one of these plants will infect all the 
others. Inoculations of cotton, egg-plant, capsicum, 
and sycamore with V. albo-atrum from the tomato have 
yielded positive results. 
It is thus apparent that many external sources of 
infection exist, and these must be carefully guarded 
against if glasshouse crops are to remain healthy. 
FUSARIUM WILT OF THE TOMATO. 
While a number of soil Fusaria are frequently found 
causing rotting of tomato roots, having gained entrance 
through wounds made by soil insects and small animals, 
the true Fusarium wilt, due to Fusariwm lycopersici Sace. 
is comparatively rare in England. It occurs only at the 
height of the summer, when the soil temperature is 
sufficiently high to enable the parasite to function. The 
relatively low temperature of glasshouse soils in this 
country is suited to development of Verticillium albo- 
airum, which grows best at a mean temperature of 
21°-22° C., but is too low for F. lycopersici, which requires 
a mean temperature of at least 28° C. before it can do 
much damage. In America, however, the soil tempera- 
ture in the chief tomato-producing regions is generally 
too high for Verticillium wilt, but is suitable for Fusariwm 
wilt. American reports show that Fusarium wilt is well 
distributed over the southern states, extending up to 
Illinois, Indiana, Ohio, and New Jersey. North of this 
it is found only occasionally. 
Symptoms of the Disease-—The external symptoms of 
Fusarium wilt are indistinguishable from those of 
Verticillium wilt. There is the same wilting, yellowing, 
and desiccation of the lower leaves, and the progression 
of these symptoms from the base of the plant upwards. 
Diseased plants have a stunted appearance, but the 
